Apple's latest iPhones will come in a bevy of colors and two distinct designs, one made of plastic and the other that aims to be "the gold standard of smart phones" and reads your fingerprint.

Apple unveiled the latest iPhone models, available on Sept. 20, during an event at its Cupertino, Calif., headquarters. The move comes as rival phones from Samsung and other manufacturers are challenging Apple's hold on the smart phone market.

The lower-cost iPhone 5C will be available in five colors -- green, blue, yellow, pink and white. CEO Tim Cook calls it "more fun and colorful" than any other iPhone. The 5C has a 4-inch Retina display and is powered by Apple's A6 chip. It also has an 8 megapixel camera, live photo filters and a rear cover that lights up.

The iPhone 5C will cost $99 for a 16 gigabyte model and $199 for a 32 gigabyte model with a two-year wireless contract. The phone is expected to help Apple boost sales in China and other areas where people don't have as much money to spend on new gadgets as they do in the U.S. and Europe.

The second phone, the 5S, is "the most forward-looking phone we have ever created," said Phil Schiller, senior vice president of worldwide marketing at Apple.